Oxidative dehydrogenation of butane

ABSTRACT

Butane may be oxidatively dehydrogenated to a mixture of 1-and 2-butenes and butadiene at high space velocities using a catalyst comprising V2O5, K2SO4, SO3 and SiO2.

United States Patent 191 Dickason [451 Oct. 21, 1975 OXIDATIVEDEHYDROGENATION OF BUTANE [75] Inventor: Alan F. Dickason, Chester, Del.

[73] Assignee: Sun Ventures, Inc., St. Davids, Pa.

[22] Filed: Nov. 23, 1973 [21] Appl. N0.: 418,499

[52] US. Cl. 260/680 E; 260/683.3

3,308,196 Bajars 260/680 D 3,308,200 3/1967 Bajars 260/680 D 3,403,1929/1968 Vadekar et a1. 260/683.3 3,770,812 11/1973 Blood et al. 260/683.3

FOREIGN PATENTS OR APPLICATIONS 998,784 7/1965 United Kingdom 260/680 EPrimary ExaminerPaul M. Coughlan, Jr. Attorney, Agent, or FirmGeorge L.Church; Donald R. Johnson; Stanford M. Back 5 7 ABSTRACT Butane may beoxidatively dehydrogenated to a mixture of l-and 2-butenes and butadieneat high space velocities using va catalyst comprising V 0 K SO,,, S0and-SiO 8 Claims, N0 Drawings This invention relates to a process forthe oxidative dehydrogenationof butane. More particularly, it relates toan improved method for the vapor phase oxidaamongst these is a catalysthaving the composition, by

weight of 9% V 29% K 80 12% S0 and 50% SiO wherein the catalyst has asurface area of about 40 m /g. One such catalyst is Catalyst No. 902,obtainable from W. P. Grace & Co. It will be understood, of

- course, that the weight percent of the catalyst compotivedehydrogenation of butane to form, a mixture of l- I and 2-butenes andbutadiene, employing a catalyst system which permits the use of spacevelocities substantially higher than those previously demonstrated byprior art.

Four references exemplifying known prior art oxidative dehydrogenationmethods for carrying out this process by the use of various catalystsare as follows: French Pat. No. 1,326,396 (sodium or lithiumphosphomolybdates); US. Pat. No. 3,119,11 l (lithium phosphomolybdate);British Pat. No. 943,941 (calcium nickel phosphate); and U.S. Pat. No.3,320,331 (A1 PO -supported molybdenum and vanadium). Each of thesemethods, while useful in the dehydrogenation of butane, is characterizedby relatively low space velocities and selectivities.

SUMMARY OF THE INVENTION It has now been found, in accordance with thepresent invention, that butane may effectively be oxidativelydehydrogenated to butenes and butadiene at high space velocities whenthere is employed a catalyst comprising a mixture of an alkali metalcompound, a vanadium oxide, and sulfur dioxide, supported on an SiOcarrier. When thus employed, this alkali metal /V.S catalyst permits theuse of gaseous hourly space velocities in the range of aboutl000-20,000hr.- i.e. velocities which are at least 5-10 times thosereported in the prior art.

DESCRIPTION OF THE INVENTION In carrying out this process, it isdesirable that the feed stream comprise substantially pure n-butane, butthis is not essential. Thus, the feed stock may contain a mixture of Cto C hydrocarbons rich in n-butane admixed with other C., hydrocarbonsas butenes, isobutenes, isobutane, as well as pentane and like compoundsderived from straight run fractions, from thermal or catalyticdehydrogenation, and/or from cracking of C and higher hydrocarbons.These other materi- 'als, when present, are substantially inert to theconditions of this reaction, and thus act as inert diluents. The butaneshould in any event, be present in the feed stream in amounts of fromabout 1 to 50 wt. percent, based on the total weight of thehydrocarbons, oxygen, and inert materials, if any, in said stream.

Oxygen, either substantially pure or in the form of air, shouldpreferably be present in stoichrometric amounts relative to the amountof butane in the feed stream, i.e. in about a 1:1 mol ratio, althoughratios of 0.1:1 to :1 may be employed if desired. However, if the oxygenconcentration is increased much beyond this latter range, competingoxidations start to take place with a resultant decrease in yield ofdesired product and an increase in the formation of C0 The oxygen ispreferably introduced into the reactor by admixing it with the feedstream before it enters the reactor.

The catalyst which has been found to be uniquely effective for thisprocess, as aforementioned, is a vanadium/alkali metal/sulfur catalyston an SiO support where the alkali metal is preferably potassium.Typical nents may be varied somewhat within the skill of the art whilestill providing the desired dehydrogenation effect. That is to say, thepercentage range of the vanadium, potassium and sulfur components of theabovedescribed catalyst may be determined routinely by'simply noting theeffect of the catalyst on the space velocity and selectivity to desiredend products. Space velocities in the range of about 1000 to 20,000hrsf, based on total gaseous feed, which provide selectivities of 50 topercent are considered within the scope of this invention.

The catalyst is generally provided in the form of pellets, so thatdesirably it is used in the reactor in the form of a fixed bed overwhich the gaseous feed stream is passed. Alternatively, of course, thecatalyst may be provided in the form of a fluidized bed, or otherconventional arrangements known in the art which permit rapid contact ofa gas and/or liquid with a particulate solid catalyst.

The reaction is conveniently carried out at temperatures of from about450to 650C, and preferably from about 500to 600C. The gas hourly spacevelocity (GHSV), as described above, should be in the range of fromabout 1000 to 20,000 hr., and preferably above 10,000 hr.". The pressurein the reactor may be any convenient, practical pressure ranging from 1to 100 atmospheres absolute. The mol ratio of butane to oxygen, asaforestated, should desirably be 1:1, although somewhat higher amountsof oxygen may be used if desired.

The invention will now be illustrated by the following examples.

EXAMPLE 1 A series of runs was carried out. In the first run 2.0 mls(2.0g) of catalyst was placed in a 6 Xl/4 inches stainless steel reactorand a gaseous mixture of nbutane (1%) and air (99%) was passed over thecatalyst bed at 630C and at a GHSV=8100 hr.'. The conversion was 17%while the selectivity to butenes and butadiene was 82% The aboveprocedure was then repeated, varying the concentration and reactionconditions. As will be seen from the above run and those in thefollowing table, the GHSV for the vanadium-potassium-sulfur catalystsystem of the invention is at least 5-10 times greater than for knowncatalyst systems. The practical significance of this substantialincrease is an increase in the spacetime-yield or the ability to operatea smaller reactor, depending upon the desires of the operator.

The invention claimed is: I

1 A process for the oxidative dehydrogenation of butane to form amixture of butenes and butadiene which comprises contacting said butanewith oxygen in the presence of an oxidative dehydrogenation catalysthaving a composition of about 9 wt. percent V about 29 wt. percent K 80about 12 wt. percent S0 and about 50 wt. percent SiO wherein thereaction is carried out at temperatures of from about 450to 650C andataGl-ISV of from about 1000 to 20,000 hr, and wherein the ratio ofoxygen to butane is in the range of from about 1:1 to :1. y

2. The process according to claim 1 wherein the catalyst comprises V 0 KSO and So supported on SiO wherein said catalyst has a surface area of40 m /g.

3. The process according to claim 1 wherein the oxygen is supplied tothe reaction in the form of air.

4. The process according to claim 1 wherein the mol ratio of oxygen tobutane 'in the feed is about 1:1.

:5. The process according to claim 1 wherein the reaction is carried outat a temperature of from about 500 the hydrocarbons, oxygen, and inertsin said stream.

1. A PROCESS FOR THE OXIDATIVE DEHYDROGENATION OF BUTANE TO FORM AMIXTURE OF BUTENES AND BUTADIENE WHICH COMPRISES CONTACTING SAID BUTANEWITH OXYGEN IN THE PRESENCE OF AN OXIDATIVE DEHYDROGENATION CATALYSTHAVIN A COMPOSITION OF ABOUT 9WT. PERCENT V2O5, ABOUT 29WT. PERCENTK2SO4, ABOUT 12WT. PERCENT SO2, AND ABOUT 50WT. PERCENT SIO2, WHEREINTHE REACTION IS CARRIED OUT AT TEMPERATURES OF FROM ABOUT 450* TO 650*CAND AT A GHSV OF FROM ABOUT 1000 TO 20,000 HR-1, AND WHEREIN THE RATIOOF OXYGEN TO BUTANE IS IN THE RANGE OF FROM ABOUT 1:1 TO 20:1.
 2. Theprocess according to claim 1 wherein the catalyst comprises V2O5 ,K2SO4and SO2supported on SiO2, wherein said catalyst has a surface areaof 40 m2/g.
 3. The process according to claim 1 wherein the oxygen issupplied to the reaction in the form of air.
 4. The process according toclaim 1 wherein the mol ratio of oxygen to butane in the feed is about1:1.
 5. The process according to claim 1 wherein the reaction is carriedout at a temperature of from about 500* to 600*C.
 6. The processaccording to claim 1 wherein the GHSV is from 5000 to 15,000 hr.
 1. 7.The process according to claim 1 wherein the butane is admixed withother C4to C6hydrocarbons.
 8. The process according to claim 1 whereinthe butane is present in the feed stream in amounts of from about 1 to50wt. percent, based on the total weight of the hydrocarbons, oxygen,and inerts in said stream.